Method of preparing alpha alpha beta-trihalogen substituted butyraldehydes



' Patented Apr. 21, 1942 METHOD OF PREPARING aafi-TRIHALOGEN SUBSTITUTED BUTYRALDEES Le Roy B. High, Detroit, Mich, assignor to The Udylite Corporation, Detroit, Mich, a corporation oi Delaware No Drawing.

12 Claims.

This invention relates to a new and improved method of making organic compounds and in particular to a method of preparing ozafl-tlihalogen substituted butyraldehydes, especially as-trichlorobutyraldehyde, and aap-tribromobutyraldehyde'.

The methods published in the literature with Application January it, 1940, Serial No. 313,688

which I am familiar are slow and cumbersome and tend to give materials which are heavily contaminated with impurities. only that the products obtained must be carefully purified but also that the yields are correspondingly low. 9

The methods previously used fall in two groups, direct chlorination of acetaldehyde or paraldehyde, and preparation of ot-CillOl'O crotonaldehyde and chlorination of it.

According to the first general method acetaldehyde is treated with dry chlorine gas first at C. and later at slowly rising temperature up to 100 C. The reaction is strongly exothermic and requires exceedingly close control, it taking iour days to completely chlorinate one pound of acetaldehyde. To the resulting crude product is added concentrated H2804, the mixture is distilled, and this product fractionated to obtain the desired mp-trlchlorobutyraldehyde.

When paraldehyde is used for starting material thesame procedure is followed except that slightly less rigorous temperature control is necessary.

The second method requires the preliminary preparation of a-ChlOlO crotonaldehyde. Several methods are known, most of them starting with acetaldehyde or acetaldehyde plus chloracetaldehyde. The u-chlorocrotonaldehyde is then treated with chlorine gas to give the desired product.

This means not The reaction formulas are probably as iollows: crn'.orr=crr.ono+r-rc1-orn.cn e1 .Cl-h.CHO

CH3.CH (C1) .CHaCHO 2612* CHLCl-HCD .0 (Cl) aCHO The details of the method are as follows:

In a vessel fitted-with a cooling coil, stirrer and thermometer, inlet tube for ll-lCl gas and Ch gas, and an outlet tube, is added about onehalf of its capacity of crotonaldehyde. Dry HG] gas is passed in while the temperature is maintained at 0-10" Q. preferably close to 0 C. The lower the temperature the less is the formation of resins and the higher is the yield. The rate. oi introduction oi i-iCl is governed by the effectiveness oi cooling, the reaction being exothermic. The emciency'oi this process is high in that the H01 is absorbed instantaneously to the end. When HCl passes through the mixture without reacting, the reaction is complete. The time of this reaction has varied between one and two hours, using a five pound batch.

It appeared to me that theaap-trichlorobutyraldehyde could easily be made from crotonaldehyde on account of the double bond and the,

high reactivity of the (Ir-hydrogen atoms. However, direct chlorination oi crotonaldehyde gave ap-dichlorobutyraldehyde only, and the mp-triv chlorobutyraldehyde could not be prepared in this substituted for the hydrogen chloride to complete the reaction the ugfi-trichloro compound.

At the end of the reaction a condenser is attached to the outlet tuba'the temperatureis raised to 50 G. and Ch g'asis added rapidly. The temperature must be at least 50 C. to make the reaction so rapidly. The temperature may go as high as 150 (3., but -i00 C. is preferred to allow water but not much compound to distill over. The condensate is separated and the top layer of water is discarded while the lower layer is returned to the reaction chamber. This reaction is also highly emcient, no Ch gas coming out until it is nearly completed. At this mint the temperature is allowed to rise. It will reach a peak at about ism- C. and then drop rather rapidly. ihen the how of chlorine isstopped. This reaction consumed from-two to 70 C, at 3.0 mm. and it C. at .8 1mm. mercury.

A small amount of resin is left in the still. The yield is at least 15% and generally higher, figured on crotonaldehyde.

'It is seen that the second reaction produces 2 mole. of HCl to make ll moi. of eap-trichlorobutyraldehyde, and that the first reaction requires only 1 mol. HCl. Therefore, after one batch of the p-product has been made with fresh HCl gas, subsequent batches can be prepared using the HCl given of! by the second reaction. We actually prefer to work with three batches at the same time. Batch 3 consists of the p-product being reacted with Cl: gas. Batch 2 consists of pchlorobutyraldehyde into whichthe gaseous byproducts, HCl and Ch, from batch 3 are led. Batch 1 is fresh crotonaldehyde through which is led any HCl gas which is not being absorbed by batch 2. The excess 1101 not absorbed during the process may be used for other purposes if desired. When batch 3 is fully reacted, it is removed to the still. Batch 2 is treated as batch 3 above, batch 1 as batch 2 above and a new batch is treated as batch 1 above. Undoubtedly arrangements could be made for continuous treatment according to the counter current principle.

Other trihalogen substituted butyraldehydes have been prepared by me in a similar manner. Thus afl-tribromobutyraldehyde was prepared by treating crotonaldehyde first with HBr gas and then with Bra, either as a gas or a liquid. The heat or reaction with Blz' is not very high, making it possible to use Bra gas without difficulties with cooling of the reaction mass. Similarly, aa-dibIOlTlO fi-chloro butyraldehyde has been prepared by treating crotonaldehyde first with HCl gas and then with Bra. aa-dlCl'llOlO pbromo butyraldehyde can be prepared by treating crotonaldehyde first with dry hydrogen bromide gas and then with chlorine (C12) The brom substituted compounds are preferably steam distilled for purification on account of their higher boiling point and lesser stability at high temperature.

The trihalogen substituted aldehydes are often used in the hydrated form as the hydrates are less corrosive and possibly more stable. To prepare .the aap-trichlorobutyraldehyde hydrate about 60 parts by weight of the aldehyde may be mixed with about 40 parts by weight of water. The mixture, is heated to about 75 C. at which temperature the solution may form two phases, either two layers or a cloudy mixture. The solution is allowed to cool when it becomes homogeneous. It comes down as a thick slurry of solid hydrate in water. The water may be separated by centrifuging. If the solution does not become homogeneous on cooling, more water may be added, the solution reheated to 75 C. and then allowed to cool again.

Glass, glass lined, lead lined, or ceramic equipment may be used throughout the process.

The prime advantages of my new process are its speed and simplicity and the high yields obtained.

I claim:

1. A method for preparing aap-trihalogen-substituted butyraldehyde comprising the steps of treating to saturation crotonaldehyde with a dry hydrogen halide from the group consisting of hydrogen chloride and hydrogen bromide, controlling the temperature of the reaction mass to control the yield of fl-halogen butyraldehyde and then halogenating the resultant product with a dry gaseous halogen from the group consisting of chlorine and bromine.

2. A method for preparing uafi-trihalogen-substituted butyraldehyde comprising the steps of treating to saturation crotonaldehyde with a dry hydrogen halide from the group consisting of hydrogen chloride and hydrogen bromide at a temperature falling within a range from approximately 0 to 10 C. and then halogenating the resultant product with a dry gaseous halogen from the group consisting of chlorine and bromine.

3. A method for preparing aap-trihalogen-substituted butyraldehyde comprising the steps of introducing a dry hydrogen halide from the group consisting of hydrogen chloride and hydrogen bromide into crotonaldehyde until the hydrogen halide passes through the mixture without reacting, and cooling the reaction mass to obtain a high yield of p-halogen butyraldehyde and then halogenating the resultant product with a dry gaseous halogen from the group consisting of chlorine and bromine.

4. A method for preparing aafi-trihalogen-substituted butyraldehyde comprising the steps of treating to saturation crotonaldehyde with a dry hydrogen halide from the group consisting of hydrogen chloride and hydrogen bromide at a temperature falling within a range from approximately 0 to 10 C. and then halogenating the resultant product with a dry gaseous halogen from the group consisting of chlorine and bromine at a temperature falling within a range from approximately C. to 150 C.

5. A method for preparing aaB-trihalogensubstituted butyraldehyde comprising the steps of introducing to saturation a dry hydrogen halide gas from the group consisting of hydrogen chloride and hydrogen bromide into crotonaldehyde while cooling the mixture to maintain the same at a temperature within a range from 0 to 10 C. to form ,B-halogen butyraldehdyde, and then introducing a dry halogen from the group consisting aldehyde with dry hydrogen chloride to saturachlorinating the resultant product with dry chlorine gas.

'1. A method for making aozfi-tl'lChlOlO butyraldehyde comprising the steps of treating crotonaldehyde with dry hydrogen chloride to saturation at a temperature falling within a range from approximately 0 to 10 C. and then chlorinatingthe resultant product with dry chlorine gas.

8. A method for making aafi-trichloro butyraldehyde comprising the steps of treating crotonaldehyde with dry hydrogen chloride to saturation at a temperature falling within a range from approximately 0 to 10 C. and then chlorinating the resultant product with dry chlorine gas at a temperature falling within a range from approximately 50 C. to C.

9. A method for making aafl-tribromo butyraldehyde comprising the steps of treating crotonaldehyde with dry hydrogen bromide to saturation, cooling the reaction mass to obtain a high yield of B-bromobutyraldehyde, and then reacting the resultant product with bromine (Bra) 10. A method for making aafi-tribromo butyraldehyde comprising the steps of treating crotonaldehyde with dry hydrogen bromide to saturation ata temeprature falling within a range from approximately 0 to 10 C. and then reacting the resultant product withbromine (Bra) at a temperature falling within a range from approximately 50 C. to 150 C.

11. A method for making m-dibromo p-chloro butyraidehyde comprising the steps of treating crotonaldehyde with dry hydrogen chloride gas to saturation, cooling the reaction mass to obtain a high yield of B-chiorobutyraldehyde and then treating the resultant product with bromine (Bra).

12. A method for making aa-dIChlOI'O p-bromo butyraldehyde comprising the steps of treating crotonaldehyde with dry hydrogen bromide gas to saturation, cooling the reaction mass to obtain a high yield of p-chlorobutyraldehyde and then treating the resultant product with chlorine (C12) r LE ROY B. HIGH.

, I Certificate of Correction Patent No. 2,280,290. April 21,1942.

LE ROY B. HIGH. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3 second column line 5, claim 12, for B-chlorobutyraldeh de read B-bromobutymidehyde' and that the said Letters Patent should be rea with this correction therein that the same maly conform to the record of the case in the Patent Ofiice.

Signed and sealed this 16th day of June, A. D. 1942.

HENRY VAN ABSDALE, Acting Commissioner of Patents. 

